V-TapGuideTM by Big Gator ToolsTM is manufactured in an ISO 9001:2000 certified facility out of a special alloyed steel that is ground and heat treated for durability. The guide holes are smooth, unlike drilled or reamed holes. Guide holes are sized for ANSI Standard Ground Taps. Standard V-TapGuide can handle tap sizes: 0-80, 1-64, 1-72, 2-56, 2-64, 3-48, 3-56, 4-36, 4-40, 4-48, 5-40, 5-44, 6-32, 6-36, 6-40, 8-32, 8-36, 8-40, 10-24, 10-32, ¼-20, ¼-28, 5/16-18, 5/16-24, 3/8-16, 3/8-24, 7/16-14, 7/16-20, ½-13, ½-20, 5/8-11, 5/8-18